Obesity: Guessing Calories Misses Mark

Action Points

Note that this survey study (hampered by a low participation rate) demonstrated that consumers systematically underestimate the calorie content of purchased fast food.

Be aware that this survey was conducted prior to the introduction of routine calorie labeling at chain restaurants.

About one in four people eating at fast-food restaurants underestimate the calorie content of their meals by at least 500 calories, a survey of over 3,000 customers at six fast-food chains suggests.

Teenagers underestimated the calories in fast-food meals by 34%, parents of school-age children by 23%, and other adults by 20%, lead author Jason Block, MD, of Harvard Medical School, and colleagues reported in BMJ.

The researchers interviewed 1,877 adults, 1,178 teens, and 330 school age children ages 3 to 15 (with their parents' help) eating at 89 fast-food restaurants across the New England region that belonged to the following chains: McDonald's, Burger King, Wendy's, KFC, Subway, and Dunkin' Donuts.

At the time of the surveys in 2010 and 2011, none of the chains routinely printed calorie content on menus.

Participants were asked to estimate the calorie content of their meal, and the figures were compared with calculations made based on their receipts.

Two-thirds of the adult participants were overweight or obese, as were 34% of the adolescents and 57% of the school-age children.

Less than one in four participants reported noticing calorie information in the restaurants that did provide them, and less than 5% reported using that information to help them choose their meal.

Overall, two-thirds of participants underestimated the calorie content of their meals. More specifically:

The mean calorie content of meals was 836 for adults, but they estimated they contained 175 fewer calories.

Teens estimated their meals provided 490 calories, which was 259 calories less than they actually contained.

School-age kids ate meals that contained a mean of 733 calories, which their parents underestimated by 175 calories.

The greater the calories in a meal, the greater the chance a participant would underestimate its actual caloric content, Block said. This finding was also observed in a smaller 2007 survey of 147 diners at food courts, he noted.

Both adults and teens who ate at Subway underestimated calorie counts more than diners at any other chain.

"These findings suggest a consistent 'health halo' for Subway in these age groups," the researchers wrote, adding that the chain's marketing and branding could explain its "healthy" label.

For example, one experiment showed that simply labeling an item as "heart healthy" led consumers to believe that the item conferred a lower risk of heart disease and stroke than similar unlabeled foods.

By extension, "Subway's positioning as a "healthier" fast food option might lead consumers to view its food as lower calorie, especially when calorie information is not readily apparent," the researchers wrote.

Block said he hopes the situation will change in light of the U.S. Patient Protection and Affordable Care Act of 2010, which included a provision that will require all restaurant chains with more than 20 U.S. sites to print calorie content on menus and menu boards.

Already, many states and U.S. cities have passed laws requiring chain restaurants to print calorie content on menus, he added.

Alice H. Lichtenstein, DSc, director of the cardiovascular nutrition laboratory at Tufts University, told The Gupta Guide that these data demonstrate the importance of having calorie information available at point of purchase.

But patients also "need continued support on how to use it. That includes educating [both adults and children] as to how many calories they typically need in a day and then how to use the available information to make menu choices," she said.

Lichtenstein suggested that educators introduce the concept into science and math classes "so children understand the relationship between calories and physical activity -- and can do the math to see how a menu item fits into their overall calorie needs."

The main limitation of the study was that more than half of eligible individuals declined to be surveyed, so participants might not represent all fast-food customers.

Do you tell your patients to check the calorie count of fast-food items? If not, they may be very surprised to learn how many calories they are consuming. Tell us what you think by clicking Add Your Knowledge below. -- Sanjay Gupta, MD

The authors reported no conflicts of interest.

Lichtenstein reported no conflicts of interest.

Reviewed by F. Perry Wilson, MD, MSCE Instructor of Medicine, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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